1. Technical Field
This invention relates to retrofit equipment for reducing the consumption of fossil fuel by a power plant using solar insolation.
2. Background of the Invention
Because of the problem of global warming, the finite supply of fossil fuels, and the stigma associated with the use of nuclear energy, interest exists in developing equipment and processes that rely on renewable energy sources, and in particular, solar energy, for power generation. Probably many decades will pass, however, before the switch from fossil fuels is complete.
It is therefore an object of the present invention to reduce the costs as well as the time involved in switching to solar based power plants by retrofitting existing fossil fueled power plants with equipment based on solar technology. This will permit the gradual replacement of existing fossil fueled power plants with minimal risk and reduced capital expenses.
Retrofit equipment according to the present invention includes an auxiliary gas turbine unit including an auxiliary compressor for compressing ambient air to produce compressed air, a solar collector that receives the compressed air for heating the same to produce heated compressed air during solar insolation, and an auxiliary turbine coupled to the auxiliary compressor and to an auxiliary generator for expanding the heated compressed air and driving the auxiliary compressor and auxiliary generator thereby producing power and hot exhaust gases. When solar insolation is available, a flow control selectively supplies the hot exhaust gases from the retrofit equipment to a boiler which is part of a conventional fossil fueled power plant. The boiler has heat exchanger coils containing water and receives hot exhaust gases for vaporizing water in the coils and producing steam which is supplied to a steam turbine coupled to a generator for expanding steam produced by the boiler, and driving the generator and producing power and expanded steam. A condenser condenses the expanded steam to condensate, and a pump returns the condensate to the boiler. When solar insolation is not available, the flow control supplies the boiler with hot gases from a primary gas turbine unit which includes a primary compressor that compresses ambient air to produce compressed air, and a combustor that receives the compressed air for burning fossil fuel and heating the compressed air to produce heated compressed air that is supplied to the primary turbine.
At night and during cloudy days or other periods of inclement weather, the primary gas turbine unit is operational, and the secondary gas turbine is quiescent. In such case, the power plant operates by burning fossil fuel. During the day, the secondary gas turbine unit operates and the primary gas turbine unit is quiescent and no fossil fuel is burned, the flow control directing exhaust gases from the secondary gas turbine unit to the boiler.
Preferably, the boiler includes a conduit having an upstream end for receiving the hot exhaust gases which flow through the conduit to a downstream end through which the gases are vented to the atmosphere. The boiler also may include a combustion chamber for burning fuel and producing hot flue gases which interact with heat exchanger coils in the conduit for heating the steam condensate and producing steam that is supplied to the steam turbine. The cooling of the flue gases introduces a temperature gradient in the flue gases flowing in the conduit; and the hot exhaust gases are introduced into the conduit at a location where the temperature of the flue gases is approximately the same as the temperature of the hot exhaust gases.
Retrofit equipment according to the present invention may also include a secondary blower for pressurizing ambient air, and a solar collector that heats pressurized ambient air produced by the last mentioned blower for producing heated ambient air. During solar insolation, a flow control selectively supplies the heated ambient air from the retrofit equipment as secondary air to a combustion chamber adapted to receive primary air and fossil fuel which burns and produces combustion products. During the night, or in cloudy weather, the secondary blower is quiescent. The power plant also includes a primary blower which introduces secondary air into the combustion chamber producing hot flue gases that are received in the upstream end of a conduit. The flue gases flow through the conduit to a downstream end through which the flue gases are vented to the atmosphere. Heat exchanger coils containing water are positioned in the conduit transfer heat in the flue gases and produce steam that is supplied to a steam turbine coupled to a generator. The steam produced by the coils expands in the turbine and drives the generator producing power and expanded steam. A condenser condenses the expanded steam to condensate; and a pump returns the condensate to the coils.